Isolation And Charaterization Of The Egyption Strains Of Bacteria Causing Salmonella Osis :

Mohamed El-sayed Aly Ibrahim

Typhoid fever remains an important public health problem in manyparts of the world. Rapid and Sensitive laboratory methods for diagnosis oftyphoid fever are essential for prompt and effective therapy (Song et al.,1993).Typhoid fever may mimic a variety of infections diseases during theinitial phase, many patients have already been on antibiotics beforeadmission, especially in countries where diagnostic facilities are limited(Hoffman et al., 1984).This study was designed to compare differentculturing and serologicaltechniques used in the diagnosis of enteric fever, to find the most rapid,sensitive and specific test for early diagnosis of typhoid fever. The study alsoaimed to evaluate the problem of salmonella multi drug resistance in Egypt.The study was done on 312 patients admitted to Abbassia feverhospital from April 2000 to April 2002. One hundred ninety one patientsproved to have typhoid fever by laboratory diagnostic tests includingdifferent diagnostic blood culturing techniques and stool culture andserologicaltests.from this study it was found that:1- The most rapid blood culture technique was lysis centrifugationculture (Isostate culture) with average time 1 day, but it was lesssensitive (43%) than conventional blood culture (55%). Isostateculture is easy to perform, needs only 30 minutes centrifugation.2- The simplest blood culturing technique was bile streptokinase culture(Clot culture) which had nearly the same sensitivity (58%) as theconventional blood culture (58%). It takes nearly the same averagetime 2.6 days as the conventional blood culture 2.8 days. Theadvantages of this technique are: (1) it is selective for salmonellaspecies and (2) it inhibits the growth of skin contaminants. (3) It iseconomic method and (4) can be performed in laboratories when bloodculture technique is not available, also (5) the separated serum can beused for serological diagnosis of typhoid fever.3- The conventional blood culture is still a seneitive blood culturetechnique (55%) but it takes more average time (2.8 days) for isolatingthe organism. It has advantage of isolating different micro-organismsother than salmonella.4- Stool culture had a limited value in the diagnosis of acute typhoidfever with sensitivity (13%).5- Serological examination for salmonella antibodies by widal tubeagglutination test helped in the diagnosis of76.4% of typhoid cases. Itis of great importance especially in young age.6- Modified widal test using 2 mercaptoethanol help in confirmation ofacute typhoid cases.7- The highest isolation rate of salmonella strains from blood (47%) wasobtained by using both conventional blood culture can detectsalmonella species within 24 hours and in case of false negative resultsdue to low number of bacteria (C.F.U. ml) we still have the chance forisolation of salmonella by the convential blood culture.8- All salmonella strains 127 (100%) isolated in the study were sensitiveto third generation cephalosporins and quinolones and only 41 (32%)were resistant to chloramphenicol which is still the drug of choice intreatment of typhoid fever in fever hospitals.usion and Recommendation1- Blood culture and serological tests should be used together in thediagnosis of typhoid fever.2- A combination of convential blood culture and isostate culture isproved to be the most rapid technique and it gives the highest isolationrate of salmonella strains. Only 10 m1blood could be enough for bothtechniques the cost will be reduced as the lytic solution will beprepared.3- Antibiotic sensitivity test should be done for all salmonella isolates todetect multi drug resistant strains (MDR).4- As only 32% of isolated salmonella strains found to be resistant tochlorampheniocol it is recommended to begin therapy of enteric feverby chloramphenicol in the proper dose and route. If the generalcondition of the patient does not improve after 5 days therapy or ifcomplications as typhoid haemorrhage or perforation or blood culturerevealed M.D.R. salmonella, the patient should be treated by eitherquinolones or third generation cephalosporins.